Energy-saving and carbon-reducing mixed butyraldehyde separation system and separation method

Abstract

The present invention provides an energy-saving and carbon-reducing mixed butyraldehyde separation system and separation method, including: a separation tower, and a distillation tower connected to the separation tower; the separation tower sidewall is provided with a feed line for conveying mixed butyraldehyde; multiple sections of first packing layers are provided in the separation tower; the feed line is located between any two adjacent sections of the first packing layers in the vertical direction; a first liquid distributor is provided above the first packing layer, the top of the separation tower is provided with a product outlet, the product outlet is connected to a tower top condensation line, the tower top condensation line includes a heat exchanger, a condensing tank, a first cooler and a first reflux tank connected in sequence, and the first reflux tank is communicated with the first liquid distributor and the distillation tower respectively. The separation system of the present invention has simple process and stable operation, effectively improves the separation efficiency of mixed butyraldehyde and the product quality of isobutyraldehyde, and can save energy and reduce carbon dioxide emissions.

Description

Technical Field

[0001] The present invention relates to the technical field of mixed butyraldehyde separation, and in particular to an energy-saving and carbon-reducing mixed butyraldehyde separation system and separation method. Background Art

[0002] Isobutyraldehyde is an important organic chemical raw material. It is a colorless, flammable, and volatile liquid at room temperature with a strong, pungent odor. Numerous fine chemical products are derived from isobutyraldehyde, such as isobutanol, neopentyl glycol, methacrylic acid, isobutyrate, and isobutyronitrile. Isobutyraldehyde is typically produced in a butyl octanol plant using propylene and synthesis gas as feedstocks, using a rhodium / triphenylphosphine complex as a catalyst, to produce a mixed butyraldehyde in an oxo reactor. The main components of the mixed butyraldehyde are a mixture of normal and isobutyraldehyde in a 10:1 mass ratio. At atmospheric pressure, the boiling points of normal butyraldehyde are 74°C and 64°C, respectively, making their separation extremely difficult. Commercially available isobutyraldehyde products are often of low purity, failing to meet downstream production needs.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The first object of the present invention is to provide an energy-saving and carbon-reducing mixed butyraldehyde separation system. The separation system separates the mixed butyraldehyde twice by arranging a separation tower and a distillation tower, which can effectively improve the purity of the obtained isobutyraldehyde; by arranging multiple layers of first packing layers and second packing layers in the separation tower and the distillation tower respectively, it helps to improve the separation efficiency of normal butyraldehyde and isobutyraldehyde, thereby improving the purity of the isobutyraldehyde product; by arranging a liquid distributor, the liquid material can be evenly distributed on the top of the packing layer, which helps to improve the mass transfer efficiency of the packing layer and ensure the operational flexibility of the packing layer; at the same time, the system can save energy and reduce carbon dioxide emissions by thermally coupling the top reboiler line of the separation tower with the bottom condenser line of the distillation tower, and using the top steam of the separation tower to provide heat for the distillation tower.

[0005] A second object of the present invention is to provide a method for separating mixed butyraldehyde, which is simple to operate and has high separation efficiency. By applying the above-mentioned separation system, the purity of the isobutyraldehyde product can be effectively improved; at the same time, through thermal coupling between the separation section and the distillation section, the steam generated by the separation of the mixed butyraldehyde is used to provide heat for the distillation of the isobutyraldehyde, which can save energy and reduce carbon dioxide emissions.

[0006] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0007] The present invention provides an energy-saving and carbon-reducing mixed butyraldehyde separation system, comprising: a separation tower and a distillation tower connected to the separation tower; a feed pipeline for conveying mixed butyraldehyde is provided on the side wall of the separation tower; a plurality of first packing layers are provided in the separation tower; the feed pipeline is located between any two adjacent first packing layers in the vertical direction;

[0008] A first liquid distributor is provided above the first packing layer, a product outlet is provided at the top of the separation tower, and the product outlet is connected to a tower top condensation pipeline, the tower top condensation pipeline includes a heat exchanger, a condensation tank, a first cooler and a first reflux tank connected in sequence, and the first reflux tank is respectively connected to the first liquid distributor and the distillation tower, so that part of the material in the first reflux tank goes to the separation tower, and the other part goes to the distillation tower;

[0009] The side wall of the distillation tower is provided with a feed port connected to the first reflux tank, and multiple sections of second packing layers are provided in the distillation tower, and the feed port is located between any two adjacent sections of the second packing layers in the vertical direction;

[0010] The specific surface areas of the first packing layer and the second packing layer are both not less than 600 m2 / m3, and the separation indexes are both not less than 5 theoretical plates / m.

[0011] In the prior art, separation of n-butyraldehyde and isobutyraldehyde is extremely difficult due to their close boiling points of 74°C and 64°C at atmospheric pressure. The purity of isobutyraldehyde products on the market is often low, failing to meet downstream production needs.

[0012] In order to solve the above technical problems, the present invention provides an energy-saving and carbon-reducing mixed butyraldehyde separation system, which separates the mixed butyraldehyde twice by arranging a separation tower and a distillation tower, thereby effectively improving the product purity; by arranging multiple layers of first packing layers and second packing layers in the separation tower and the distillation tower respectively, and limiting the specific surface area and separation index of the first packing layer and the second packing layer, the theoretical plate number can be increased, the pressure drop can be reduced, and the bottom temperature of the tower can be reduced by more than 10°C. At the same time, the generation of by-products can be effectively prevented, the separation efficiency can be improved, and the required energy consumption can be reduced; by arranging a first liquid distributor and a second liquid distributor, they can cooperate with the first packing layer and the second packing layer respectively, and the reflux liquid material can be evenly distributed on the top of the packing layer, which helps to improve the mass transfer efficiency of the packing layer and ensure the operational flexibility of the packing layer.

[0013] Preferably, a bottom reboiler line is provided at the bottom of the distillation tower, with its inlet connected to the material outlet at the bottom of the distillation tower and its outlet connected to the bottom of the distillation tower. The bottom reboiler line and the top condenser line are coupled via the heat exchanger, allowing the overhead vapor from the separation tower to provide heat to the distillation tower. This arrangement allows the material gas flowing out of the separation tower product outlet to exchange heat with the liquid flowing out of the distillation tower bottom, effectively saving energy.

[0014] Preferably, a plurality of first trays are provided below the first packing layer, the first trays being vertically located above the connection point where the reflux line is connected to the sidewall of the separation tower. The first trays can cooperate with the first packing layer to promote the separation of n-butyraldehyde and isobutyraldehyde.

[0015] Preferably, a plurality of second trays are provided below the second packing layer, and the second trays are vertically located above the connection point between the material outlet and the distillation column. The second trays can cooperate with the second packing layer to promote the separation of n-butyraldehyde and isobutyraldehyde.

[0016] Preferably, an isobutyraldehyde outlet is provided at the top of the distillation tower, and the isobutyraldehyde outlet is sequentially connected to a condenser and a second reflux tank. The isobutyraldehyde discharged from the isobutyraldehyde outlet is condensed by the condenser and then flows into the second reflux tank.

[0017] Preferably, the outlet of the second reflux tank is connected to a second cooler and an isobutyraldehyde storage tank in sequence, and the outlet of the second reflux tank is also connected to a second liquid distributor; the second liquid distributor is located above the second packing layer; a part of the isobutyraldehyde in the second reflux tank is refluxed into the distillation tower through the second liquid distributor, and the other part is cooled by the second cooler and then flows into the isobutyraldehyde storage tank.

[0018] Preferably, a reflux pipeline is provided at the bottom of the separation tower, the inlet of the reflux pipeline is connected to the bottom of the separation tower, and the outlet is connected to the kettle of the separation tower; a kettle reboiler is provided on the reflux pipeline.

[0019] Preferably, a n-butyraldehyde outlet is provided at the bottom of the distillation tower, and the n-butyraldehyde outlet is connected to a n-butyraldehyde storage tank.

[0020] Preferably, the bottom of the separation tower is connected to the n-butyraldehyde storage tank, and a third cooler is provided between the bottom of the separation tower and the n-butyraldehyde storage tank.

[0021] Preferably, the first packing layer and the second packing layer are both wall-less flow structured packing layers.

[0022] Preferably, the first liquid distributor and the second liquid distributor are both infinite point liquid distributors.

[0023] Preferably, the condensing tank is provided with a non-condensable gas outlet, and the non-condensable gas is discharged through the non-condensable gas outlet.

[0024] Preferably, the first tray and the second tray are valve trays.

[0025] In fact, the mixed butyraldehyde separation system of the present invention can effectively save energy and reduce carbon emissions compared to the prior art. Specifically, based on 0.8MPa (G) saturated steam calculation, the theoretical energy consumption (calculated based on 0°C water) for producing one ton of steam is 662766kcal. According to this calculation, one ton of steam consumes 94.7 kg standard coal per ton of steam. If the steam boiler efficiency is 70%, the actual coal consumption is 135 kg standard coal per ton of steam. For every ton of standard coal burned by an industrial boiler, 2620 kg of carbon dioxide is produced. After conversion, 353.7 kg of carbon dioxide is released for every ton of steam produced. The separation system of the present invention uses a thermal coupling process as a whole to heat the distillation tower using the material steam generated by the separation tower. The steam unit consumption drops by 30-40%, and the amount of carbon dioxide produced is reduced accordingly, thereby effectively reducing carbon emissions.

[0026] The present invention also provides a mixed butyraldehyde separation method, comprising: separating the mixed butyraldehyde into normal butyraldehyde and isobutyraldehyde crude products, and distilling the isobutyraldehyde crude products to obtain isobutyraldehyde.

[0027] Preferably, the separation temperature of the mixed butyraldehyde is 100-140°C and the pressure is 0.1-0.5 MPa; the distillation temperature of the crude isobutyraldehyde product is 80-100°C and the pressure is 0.005-0.2 MPa. Furthermore, the separation temperature of the mixed butyraldehyde is 113°C and the pressure is 0.25 MPa, and the distillation temperature of the crude isobutyraldehyde product is 91°C and the pressure is 0.011 MPa.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The energy-saving and carbon-reducing mixed butyraldehyde separation system of the present invention can effectively improve the purity of the product by providing a separation tower and a distillation tower to separate the mixed butyraldehyde twice;

[0030] (2) By arranging multiple layers of first packing layers and second packing layers in the separation tower and the distillation tower respectively, the number of theoretical plates can be increased and the pressure drop can be reduced, thereby reducing the bottom temperature by more than 10°C. At the same time, the formation of by-products can be effectively prevented, the separation efficiency can be improved, and the required energy consumption can be reduced;

[0031] (3) By setting the first liquid distributor and the second liquid distributor, they can cooperate with the first packing layer and the second packing layer respectively to evenly distribute the mixed butyraldehyde on the top of the packing layer, which helps to improve the mass transfer efficiency of the packing layer and ensure the operational flexibility of the packing layer;

[0032] (4) By thermally coupling the reboiler line at the top of the separation tower with the condenser line at the bottom of the distillation tower, the steam at the top of the separation tower can be used to provide heat for the distillation tower, which can save energy and reduce carbon dioxide emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0034] Figure 1 This is a schematic structural diagram of the energy-saving and carbon-reducing mixed butyraldehyde separation system provided in Example 1 of the present invention;

[0035] Figure 2 This is the effect curve of the number of theoretical plates of the tower on the isobutyraldehyde content in the bottom of the tower in Example 1 of the present invention;

[0036] Figure 3 This is the influence curve of the reflux ratio on the isobutyraldehyde content in the bottom of the tower in Example 1 of the present invention.

[0037] in:

[0038] DETAILED DESCRIPTION

[0039] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0040] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0041] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0042] In order to more clearly illustrate the technical solutions of the present invention, specific embodiments are provided below for illustration.

[0043] Example 1

[0044] See Figure 1 As shown, this embodiment provides an energy-saving and carbon-reducing mixed butyraldehyde separation system, comprising: a separation tower 10, and a distillation tower 80 connected to the separation tower 10; a feed pipeline 140 for conveying mixed butyraldehyde is provided on the side wall of the separation tower 10; a plurality of first packing layers 102 are provided in the separation tower 10; the feed pipeline 140 is located between any two adjacent first packing layers 102 in the vertical direction; specifically, the feed pipeline 140 is located between the two uppermost first packing layers 102 in the vertical direction;

[0045] A plurality of first trays 103 are provided below the first packing layer 102 , and the first trays 103 are located above the connection point where the reflux line 105 is connected to the side wall of the separation tower 10 in the vertical direction.

[0046] A reflux line 105 is provided at the bottom of the separation tower 10 , the inlet of the reflux line 105 is connected to the bottom of the separation tower 10 , and the outlet is connected to the kettle of the separation tower 10 ; a kettle reboiler 20 is provided on the reflux line 105 .

[0047] Continue reading Figure 1A first liquid distributor 101 is provided above the first packing layer 102, and a product outlet 104 is provided at the top of the separation tower 10. The product outlet 104 is connected to the top condensation pipeline of the tower. The top condensation pipeline of the tower includes a heat exchanger 70, a condensation tank 60, a first cooler 50 and a first reflux tank 40 connected in sequence. The first reflux tank 40 is respectively connected to the first liquid distributor 101 and the distillation tower 80; part of the material in the first reflux tank 40 is refluxed to the separation tower 10 through the first liquid distributor 101, and the other part flows into the distillation tower 80.

[0048] The condensation tank 60 is provided with a non-condensable gas outlet, through which the non-condensable gas is discharged.

[0049] Specifically, a feed port connected to the first reflux tank 40 is provided on the side wall of the distillation tower 80, and multiple sections of second packing layers 803 are provided in the distillation tower 80, and the feed port is located between any two adjacent sections of the second packing layers 803 in the vertical direction; further, the feed port is located between the two top sections of the second packing layers 803 in the vertical direction.

[0050] A plurality of second trays 804 are provided below the second packing layer 803 . The second trays 804 are located vertically above the connection point between the material outlet 805 and the distillation tower 80 .

[0051] A bottom reboiler line is provided at the bottom of the distillation tower 80, the inlet of the bottom reboiler line is connected to the material outlet 805 at the bottom of the distillation tower 80, and the outlet is connected to the kettle of the distillation tower 80; the bottom reboiler line and the top condenser line are coupled to each other through the heat exchanger 70 so that the top steam of the separation tower provides heat for the distillation tower.

[0052] An isobutyraldehyde outlet 801 is provided at the top of the distillation tower 80. The isobutyraldehyde outlet 801 is sequentially connected to a condenser 100 and a second reflux tank 110. The isobutyraldehyde discharged from the isobutyraldehyde outlet 801 is condensed by the condenser 100 and flows into the second reflux tank 110. The outlet of the second reflux tank 110 is sequentially connected to a second cooler 120 and an isobutyraldehyde storage tank 130. The outlet of the second reflux tank 110 is also connected to a second liquid distributor 802; the second liquid distributor 802 is located above the second packing layer 803; a portion of the isobutyraldehyde in the second reflux tank 110 is refluxed into the distillation tower 80 via the second liquid distributor 802, and the other portion is cooled by the second cooler 120 and flows into the isobutyraldehyde storage tank 130.

[0053] In this embodiment, a n-butyraldehyde outlet 806 is provided at the bottom of the distillation tower 80, and the n-butyraldehyde outlet 806 is connected to the n-butyraldehyde storage tank 90. ​​The bottom of the separation tower 10 is connected to the n-butyraldehyde storage tank 90, and a third cooler 30 is provided between the bottom of the separation tower 10 and the n-butyraldehyde storage tank 90.

[0054] To ensure the separation effect, the specific surface area of ​​the first packing layer 102 and the second packing layer 803 is not less than 600m 2 / m 3 , the separation index is not less than 5 theoretical plates / m; Specifically, the specific surface area of ​​the first packing layer 102 and the second packing layer 803 in this embodiment is 600m 2 / m 3 , the separation index is 5 theoretical plates.

[0055] In this embodiment, the first packing layer 102 and the second packing layer 803 are both wall-less flow structured packing layers, specifically wall-less flow structured packing layers SP-B2; the first tower plate 103 and the second tower plate 804 are both valve tower plates, specifically valve tower plates SVT; the first liquid distributor 101 and the second liquid distributor 802 are both infinite point liquid distributors, specifically infinite point liquid distributors LD-II.

[0056] During the reaction, the mixed butyraldehyde enters the separation tower 10 through the feed line 140, and the crude isobutyraldehyde product enters the first reflux tank 40 after being cooled by the heat exchanger 70, the condenser 60 and the first cooler 50. A portion of the crude isobutyraldehyde product in the first reflux tank 40 is refluxed to the separation tower 10 for further separation, and the other portion enters the distillation tower 80 for distillation.

[0057] A portion of the n-butyraldehyde separated from the separation tower 10 is heated and vaporized through the reflux line 105 and refluxed into the separation tower 10 , while the other portion is cooled through the third cooler 30 and flows into the n-butyraldehyde storage tank 90 .

[0058] The distillation tower 80 performs distillation and purification on the crude isobutyraldehyde. The purified isobutyraldehyde is condensed in the condenser 100 and enters the second reflux tank 110. A portion of the isobutyraldehyde is refluxed into the distillation tower 80 for further distillation, and the remaining portion is cooled in the second cooler 120 and flows into the isobutyraldehyde storage tank 130.

[0059] A portion of the n-butyraldehyde separated from the distillation tower 80 is heated in the heat exchanger 70 and then flows back to the distillation tower 80 , while the other portion flows into the n-butyraldehyde storage tank 90 .

[0060] The process simulation calculation is based on the mixed butyraldehyde feed composition. The influence curve of the theoretical plate number and reflux ratio on the isobutyraldehyde content in the tower is shown in Figure 2-3 The figure shows that the isobutyraldehyde content in the bottom of the column is very sensitive to the number of theoretical plates, while when the operating reflux ratio is greater than 2.6, the isobutyraldehyde content in the bottom of the column is insensitive to the reflux ratio. Therefore, while maintaining the same column height, increasing the number of theoretical plates by using packing layers can effectively improve the separation efficiency of mixed butyraldehyde and increase the purity of the isobutyraldehyde product.

[0061] Example 2

[0062] The only difference between this example and Example 1 is that the first tray 103 and the second tray 804 are not provided.

[0063] Comparative Example 1

[0064] The only difference between this example and Example 1 is that the first packing layer 102 and the second packing layer 803 are replaced by tower plates.

[0065] Experimental example

[0066] The separation systems in Examples 1-2 and Comparative Example 1 were used to separate the mixed butyraldehyde, and the isobutyraldehyde content in the separation tower kettle and the purity of the isobutyraldehyde separated from the top of the distillation tower were tested and statistically analyzed. The structure is shown in the following table.

[0067] In Table 1, the temperature in the separation tower is 100° C. and the pressure is 0.1 MPa; the temperature in the distillation tower is 80° C. and the pressure is 0.005 MPa.

[0068] In Table 2, the temperature in the separation tower is 113°C and the pressure is 0.25 MPa; the temperature in the distillation tower is 91°C and the pressure is 0.011 MPa.

[0069] In Table 3, the temperature in the separation tower is 140°C and the pressure is 0.5 MPa; the temperature in the distillation tower is 100°C and the pressure is 0.2 MPa.

[0070] Table 1

[0071]

[0072] Table 2

[0073]

[0074] Table 3

[0075]

[0076] The separation system of the present invention can achieve efficient separation of isobutyraldehyde. The purity of the separated isobutyraldehyde meets the industry standard HG / T4965-2016, which stipulates a purity of greater than 99.2 wt% for superior isobutyraldehyde. This solves the problem of low isobutyraldehyde purity, while also providing a simple process and stable operation. Compared to traditional processes, the device's production capacity can be increased by 30%, steam consumption per unit can be reduced by 30-40%, and energy consumption can be reduced by 35-45%.

[0077] In summary, the separation system of the present invention has a simple process and stable operation, effectively improves the separation efficiency of mixed butyraldehyde and the product quality of isobutyraldehyde, and can save energy and reduce carbon dioxide emissions.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An energy-saving and carbon-reducing mixed butyraldehyde separation system, characterized in that: include: A separation tower and a distillation tower connected to the separation tower; a feed pipeline for conveying mixed butyraldehyde is provided on the side wall of the separation tower; a plurality of first packing layers are provided in the separation tower; the feed pipeline is located between any two adjacent first packing layers in the vertical direction; A first liquid distributor is provided above the first packing layer, and a product outlet is provided at the top of the separation tower, and the product outlet is used to output the crude isobutyraldehyde product; the product outlet is connected to a tower top condensation pipeline, and the tower top condensation pipeline includes a heat exchanger, a condensation tank, a first cooler and a first reflux tank connected in sequence, and the first reflux tank is respectively connected to the first liquid distributor and the distillation tower, so that part of the material in the first reflux tank goes to the separation tower, and the other part goes to the distillation tower; The side wall of the distillation tower is provided with a feed port connected to the first reflux tank, and multiple sections of second packing layers are provided in the distillation tower, and the feed port is located between any two adjacent sections of the second packing layers in the vertical direction; The specific surface area of ​​the first packing layer and the second packing layer is not less than 600m 2 / m 3 , the separation index is not less than 5 theoretical plates / m; A bottom reboiler pipe is provided at the bottom of the distillation tower, the inlet of the bottom reboiler pipe is connected to the material outlet at the bottom of the distillation tower, and the outlet is connected to the bottom of the distillation tower; the bottom reboiler pipe and the top condenser pipe are coupled to each other through the heat exchanger so that the top steam of the separation tower provides heat for the distillation tower; A plurality of second trays are provided below the second packing layer, and the second trays are located above the connection point between the material outlet and the distillation tower in the vertical direction; The separation temperature in the separation tower is 100-140°C and the pressure is 0.1-0.5MPa; The top of the distillation tower is provided with an isobutyraldehyde outlet, and the bottom is provided with a normal butyraldehyde outlet. The distillation temperature in the distillation tower is 80-100° C. and the pressure is 0.005-0.2 MPa.

2. The mixed butyraldehyde separation system according to claim 1, characterized in that: The isobutyraldehyde outlet is connected to a condenser and a second reflux tank in sequence. The isobutyraldehyde discharged from the isobutyraldehyde outlet is condensed by the condenser and then flows into the second reflux tank.

3. The mixed butyraldehyde separation system according to claim 2, characterized in that: The outlet of the second reflux tank is connected to the second cooler and the isobutyraldehyde storage tank in sequence, and the outlet of the second reflux tank is also connected to the second liquid distributor; the second liquid distributor is located above the second packing layer; part of the isobutyraldehyde in the second reflux tank is refluxed into the distillation tower through the second liquid distributor, and the other part is cooled by the second cooler and then flows into the isobutyraldehyde storage tank.

4. The mixed butyraldehyde separation system according to claim 1, characterized in that: A reflux pipeline is provided at the bottom of the separation tower, the inlet of the reflux pipeline is connected to the bottom of the separation tower, and the outlet is connected to the kettle of the separation tower; a kettle reboiler is provided on the reflux pipeline.

5. The mixed butyraldehyde separation system according to claim 4, characterized in that: A plurality of first tower plates are arranged below the first packing layer, and the first tower plates are located above the connection point where the reflux line is connected to the side wall of the separation tower in the vertical direction.

6. The mixed butyraldehyde separation system according to claim 1, characterized in that: The n-butyraldehyde outlet is connected to a n-butyraldehyde storage tank.

7. The mixed butyraldehyde separation system according to claim 6, characterized in that: The bottom of the separation tower is connected to the n-butyraldehyde storage tank, and a third cooler is provided between the bottom of the separation tower and the n-butyraldehyde storage tank.

8. A method for separating mixed butyraldehyde, characterized in that: The mixed butyraldehyde separation system according to any one of claims 1 to 7 is used; the method comprises: separating the mixed butyraldehyde into normal butyraldehyde and crude isobutyraldehyde products, and distilling the crude isobutyraldehyde product to obtain isobutyraldehyde.

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